The instant invention relates to a wear protection layer on the basis of a synthetic resin matrix, to a method for the production thereof and to the use thereof.
It is well known to seal surfaces of furniture, floors, ceramics or other articles of daily use, which consist of the most versatile materials, so as to protect the surface on the one hand and so as to give a decorative appearance to the surface on the other hand. The most versatile matrix materials are used to reduce the sensitivity of the surface to mechanical, thermal or chemical stress and to give it a decorative appearance at the same time, whereby these are oftentimes duroplastic, thermoplastic or elastomer synthetic materials, which can be hardened by means of exposure to temperature or by means of irradiation.
It is also well known to give a decorative appearance to the surfaces of furniture, floors, etc. by applying so-called high-pressure laminates. The laminate thereby mostly consists of three different layers, namely a colored or imprinted décor paper, a transparent overlay paper located thereabove and one or a plurality of so-called core papers, which are located therebelow and which serve as support for the décor paper and the overlay paper. Typically, all three papers are impregnated with a heat-hardenable synthetic resin.
Further embodiments are known, in the case of which the décor paper is covered with an overlay paper and is hot pressed directly onto a wood fiber board. A method is also known, in the case of which the décor is imprinted directly onto a pretreated and primed wood fiber board and the surface is subsequently coated with a clear lacquer on the basis of acrylates, to which aluminum oxide is added, and is then hardened by means of UV light.
In particular melamine resins, urea resins, phenol resins, acrylate resins, epoxy resins, polyester resins, aminoplasts, polyurethanes as well as mixtures of these components are suitable as heat and/or irradiation-hardenable synthetic resins or lacquer systems, respectively. In the past, attempts were made repeatedly to increase the abrasion resistance of a laminate by storing hard material particles into the resin layer, with which a core-impregnated décor paper is coated, for example.
For instance, a plurality of publications describes corresponding methods for producing abrasion resistant décor layers or laminates, respectively, in the case of which mainly particles based on aluminum oxide are used as suitable hard material particles for producing wear resistant décor layers. The preferred range for the average grain size of the particles is thereby typically between 1 μm and 80 μm.
For instance, U.S. Pat. No. 3,928,706 A describes the production of wear resistant décor layers, which consist of a core paper, a décor paper, a wear layer and an overlay paper. The wear layer consisting of a heat-hardenable synthetic resin comprising hard materials, which are finely distributed therein and which encompass a Mohs hardness of at least 7, is applied either onto a surface of the décor or of the overlay paper. All three papers are impregnated with a heat-hardenable synthetic resin and are processed to form a uniform laminate in the typical manner, in that they are pressed between highly polished die plates at temperatures of approx. 150° C.
EP 0 519 242 A1 describes a wear protection layer of special clarity and brilliance, which can be obtained in that the décor paper is provided with a wear layer, which contains hard materials coated with silane. The processing into the finished laminate also takes place herein by means of pressing.
In all cases, the production of wear resistant laminate surfaces by storing hard materials on décor papers or also the direct coating with hard material-filled liquid overlays leads to a considerable problem in the case of the end production of the laminates, because the surfaces of the die plates or press belts are scratched and are made unusable relatively quickly due to the contact with the hard material particles in response to the discontinuous operation using presses with highly-polished die plates as well as in response to the continuous operation with press belts. The die plate wear is thus a quite substantial cost factor in response in response to the production of wear resistant décor layers.
Attempts to solve the wear problem in response to the production mostly resulted in the avoidance of the direct contact between hard material particles and die plates by means of suitable measures.
For instance, WO 2006/013469 A1 describes a method in the case of which a first layer of the hard material particles is initially applied onto a substrate and a second polymer layer is subsequently applied onto the first abrasion resistant layer, in which particles are stored, which encompass a lower hardness, but also a lower abrasiveness, for which glass spheres or glass fibers can be used.
EP 1 319 524 A1 describes a similar way in the case of which the object is solved in that lacquer or impregnating resin systems are used, which include glass spheres, for example, which encompass a useable hardness, but a low intrinsic abrasiveness, as mentioned above.
WO 02/066265 A1 describes a method for producing a décor paper, in the case of which abrasion resistant particles, such as aluminum oxide or silicon carbide, e.g., which are stored in the resin, are coated with glass spheres or glass fibers in an additional operating step, so as to thus avoid the direct contact of the aluminum oxide or silicon carbide particles with the mirror surface of the press and so as to avoid damages. The spheres or fibers are to thereby ensure the desired distance between the abrasion resistant particles and the die plate or the press belt, respectively.
EP 1 339 545 B1 describes a wear protection layer on the basis of synthetic resin, wherein substantially cutting edge-free round solid material particles in the form of spheres comprising a lower hardness than that of the hard material particles are stored in the synthetic resin system in addition to the hard material particles. The average particle diameter of the spheres is thereby greater than the average grain diameter of the hard material particles. It is attained with this that the direct contact of the press die surface with the hard material particles is avoided and the round solid material particles quasi act as spacers.
The above-described methods, which mainly serve to protect the press dies, have the disadvantage that even though the tools, press dies or press belts are now saved by storing particles comprising a low intrinsic abrasiveness in the outer area of the décor layer, experience shows that the wear resistance of the layer is reduced.
WO 2008/128702 A1 describes a wear protection layer, in the case of which the hard material particles responsible for the wear resistance are partially replaced by less hard, substantially cutting edge-free and round solid material particles, such as full spheres made of glass, e.g. Provision is thereby made for the particle diameters of the round solid material particles to be the same or smaller than the particle diameters of the hard material particles. In so doing, the wear resistance of the décor layer remains up to a certain degree of substitution, wherein the relatively expensive hard material particles can be partially replaced by cheaper glass spheres, and a certain protection for the press dies is attained at the same time. However, the use of glass spheres with the same size or smaller has the disadvantage that overlay papers must still be used again additionally for the protection of the press dies, which in turn increases the costs of the production method.